Rain water harvesting and slow sand water filters

Update November 25, 2013:

An important observation regarding 5 gallon slow sand filters: They are highly susceptible to disruption from freezing temperature. For the past week all of the 5 gallon filters have been frozen. The temps here, in the forest, have been in the mid 20’s (deg. F) at night and barely above freezing during the day. All work on these 5 gallon filters must now start over, as freezing expands the the surface of the sand and effectively disrupts any biolayer that has formed.  The larger filters, with unrestricted continuous flow,  did not freeze. They are still running.

Update November 15, 2013:

I’ve made another critical mistake on these small filters. I forgot to “rough up” the inside surface of the buckets  with coarse sandpaper.  The inside walls of the buckets i am using are smooth, very smooth – in fact far too smooth, because they are new. This is not good, for filters. (this likely would not happen with some recycled containers, as they may already have been “roughed up” on the inside.)The sides of the container must be rough so the biofilm has a randomly rough surface, similar to sand surface,  to cling to. The problem with the smoothness is that its “slipperiness”allows untreated water to slip down the inside of the bucket between the sand and the smooth plastic surface.  As the schmutzdecke matures on the sand surface it slows down the water flow, but between the sand and the bucket inside wall the schmutzdecke can’t form as fast, or as well, because of the lack of surface area on the smooth surface of the bucket. So the microbes and silt that should remain on the top surface of the sand slip through around the sides of the bucket. This would explain why the output water has been showing more coliform instead of less.  This will continue to happen until the biofilm is able to seal up the space between the sand and the smooth inside of the bucket. The seal will most likely be so fragile, that if the bucket is accidentally bumped, the seal will be broken and untreated water will flow past the sand and into the output.  The irony here is that I had this same problem with the larger filters. I forgot to rough up the inside of the containers. Since I had fixed that problem in the larger filters, they are working much better.

On September 16, 2013 we described an experimental ( very small ) slow sand filter setup that was started running here at that time. We have used 5 gallon buckets as the filter container in both cases (filter 10a and filter 10b) with a sand depth of 9.5 inches. Filter 10b was started October 16.

To summarize the results so far ( this is my opinion based on observation and preliminary field tests): Some water quality improvement has been noted, both biological and physical. Ecoli are removed. Coliform is reduced slightly, but not eliminated. Initially, water clarity and color was improved slightly. The degree of improvement has not increased.

After 7 weeks of running time, it appears that a slow sand filter setup in a 5 gallon bucket using .25mm effective size sand with a flow rate of 1 cup per minute  is, at the very best, only marginally effective at filtering roof water from the roof at this location.  A better situation may be to use fine sand (.15mm effective size) as an absolute must, and a flow rate of less than 1/2 cup per minute. However do look at the results (scroll down at the following link to see the image) of the most recent field test on filter 10a. in the original post. The output water quality has become exceedingly more contaminated as time goes on. Compare this to the 38 inch deep filter 5 tests shown. The filter 5 output is nearly perfect.  Fiter 5 uses the same water source as filter 10a.

After 4 years of college where I learned (hopefully) how to write about what I observe; and following that, close to 7 years of designing, building, studying, and operating small scale slow sand water filters (often called biological sand water filters); some information has become self-evident:

1. With some basic understanding, common sense, and willingness to pay attention to simple maintenance; It is possible to produce extremely high quality water with a “do it yourself” small scale biological slow sand water filter.

2. Continuous flow of water from the same source through a small slow sand filter will result in the highest quality output. (use an overflow to capture the water that does not flow through the filter immediately, and then just re-introduce it again, no fancy expensive high tech stuff is needed if the operator is willing to add the water manually)

3. Finer sand in a small slow sand filter produces the highest quality output as compared to coarser sand, which does not.

4. A slow flow through a small biological sand water filter produces the best output as opposed to a rapid flow, which does not.

5. Thoroughly washed sand produces better output water, than un-washed sand.

6. It is possible to sift your own sand using inexpensive commonly available sand, resulting in sand size quality that comes close to duplicating “manufactured filter sand”.

7. The output from a “do it yourself” small slow sand filter will vary considerably, depending on the surroundings, input water, and attention to maintenance.

8. Highly turbid (cloudy) water will clog a small slow sand filter very quickly; within days, or even hours.

9. “Cleaning” a small slow sand filter by “wet harrowing” is very easy and takes very little time.

All of the specific details regarding implementation of these concepts can be found in this blog, and the three other water filtration websites that are associated with it.

To determine the uniformity coeffient of sand (from a chosen source):

First: Take a small sample of the sand and determine the sand grain size (wire mesh hole size opening) at which 60% of this small sample‘s weight passes through the holes in a sifting appratus such as wire mesh, and 40% of it does not pass through the holes in that same sifting apparatus.

Second: Then take another small sample of the same sand. Make sure it is the same weight as the first small sample. Then determine the sand grain size (wire mesh hole size opening) at which 10% of this small sample‘s weight passes through the holes in a another sifting appratus such as wire mesh, and 90% of it does not pass through the holes in the same sifting appratus used in this second sifting operation.

Use the same mesh pattern for the first and second operation. However, the mesh opening sizes in the first operation will be different than the mesh opening sizes in the second operation.

Then know that for an equal weight of sand the uniformity coefficient equals:

the sand grain size at which 60% goes through and 40 % is retained
divided by
the sand grain size at which 10% goes through and 90% is retained

A rudimentary test was done yesterday, October 2, 2013,  to evaluate water clarity on all of the filters running here. The filters that have the least restricted output flow also have the clearest water output. Two of the filters that have the output running into storage did not have enough ventilation and the storage containers did not have appropriate overflow outlets; these two had the cloudiest output. The three filters with continuous flow into vented storage have the clearest output. Not sure exactly why yet. . .    more later.

Filter 5, the one with the cloudiest output, was modified so the storage has an overflow drain that is lower (closer to the ground) than  the filter output. As I checked this system out it became apparent that there was very little, if any, flow through the filter because the storage was full and there was nowhere for the water to go as it flowed out of the filter. As of October 2, 2013, water is free flowing out of the filter into the storage containers.

We have had water collected from a composition roof at this location tested by an EPA certified laboratory. The water passed (actually far surpassed) all epa, and local requirements for potable water purity after being run through a small slow sand water filter (filter 1). Composition roofing material can be used for rainwater collection. An excellent study was done regarding this issue by the Texas Water Development Board (P.O. Box 13231, Capitol Station Austin, Texas 78711-3231), that further confirms our results. “Effect of Roof Material on Water Quality for Rainwater Harvesting Systems”
Report by:
Carolina B. Mendez
Brigit R. Afshar
Kerry Kinney, Ph.D.
Michael E. Barrett, Ph.D.
Mary Jo Kirisits, Ph.D.

A new (composition) roof has been installed on the water collection surface that feeds 3 of the slow sand filters in operation here (filter 1,  filter 5,  and the (very small) diy experimental filter mentioned in the extensive post before this one. According to the best information we have, this roofing material does not have moss killer (zinc) embedded in it. As time passes, we will do tests on the water for copper, and zinc compounds – as these are the most common chemicals used to kill algae, and moss. The MSDS reports that the roofing material contains :

Granules – 20 – 45 NE NE NE

Limestone 1317-65-3 25 – 45 5 mg/m3 – resp.15 mg/m3 – total3 mg/m3 – resp.10 mg/m3 – totalREL: 5 mg/m3 –resp.10 mg/m3 – total

Oxidized Asphalt 64742-93-4 10 – 30 NE 0.5 mg/m3(inhalable fraction, as benzene-soluble aerosol)5 mg/m3 – ceiling (15 min. fumes)

Crystalline Silica 14808-60-7 0 – 10 10 mg/m3 / (% SiO2 + 2) – resp.0.025 mg/m3 REL: 0.05 mg/m3 –resp.

Fiberglass Mat 65997-17-3 1 – 3 1 f/cc – resp. 1 f/cc – resp. REL: 5 mg/m3 – total fibers

Titanium Dioxide 13463-67-7 0 – 4 15 mg/m3 – total 10 mg/m3 – total REL: lowest feasible concentration

It is a “50 year” roof. So far, the water has been quite “clear”, (non-turbid) and not discolored. The shingles are: Timberline® Ultra HD™ Lifetime Shingles

Biological sand water filtration (slow sand water filtration) works mainly because of living things we can’t see with our eyes. If water flows slowly enough through sand, it can be cleansed by these living microscopic organisms with help from gravity and small particles of sand.

To more clearly understand why (and how) biological sand water filters work, know that water is recycled “naturally” by its interaction with living organisms, ultraviolet light (sunlight) , and physical filtration through earth (usually called soil or dirt) and porous rocks. Be aware that this earth is alive all over and that microscopic life exists almost everywhere here on this planet. Lots of these tiny organisms are in water and most of them are harmless to healthy people. Without these organisms, we would not survive. Understand that without water, there would be no life as we know it here on this planet. To be comfortable with the idea that water can flow through “dirt” and come out clean; a new way of thinking may be necessary for lots of people.

To attain this mindset, try to stop thinking of the stuff on the top 15 inches of this earth as “dirt”, or re-define “dirt” (maybe referring to industrial pollution as “dirt” would help); and remember where our food comes from – its NOT the grocery store. All of what we eat depends on land and water – the surface of mother earth. Potatoes, radishes, carrots, garlic, onions, beets, yams, sweet potatoes, shallots, ginger and peanuts, to name just a few, all come right out of the “dirt”. Ok, lets stop calling mother earth “dirt”. All come from mother earth. We may buy them at the “grocery store”,  but they all come to us courtesy of mother earth.

In a biological sand water filter, micro-organisms, most of them harmless, grow and cling to the surface of sand particles inside the filter. As water flows slowly through the sand, these organisms form a biofilm that traps and consumes other micro-organisms including those that make people sick. In recent history (the past 150 to 200 years) it has been known (documented) that this type of filtration works in man-made filter systems. In the past 20 years, scientists have discovered a lot about why and how it works.

Some of the details are in the rest of the pages of this blog, and may also be found easily on the internet by doing a search for “slow sand water filter”.

My references can be found here:

http://www.slowsandfilter.org/lit_cited.html

and here:

http://www.shared-source-initiative.com/biosand_filter/references.html

Also included my references:

7 years of experience building and testing slow sand water filters documented here:

http://www.slowsandfilter.org/index.html

http://www.shared-source-initiative.com/biosand_filter/biosand.html

http://www.roofwaterharvesting.org/

Filter 4 and 5 now have re-circulation systems installed. Both of these filters had failed miserably in April/May of this year due to lack of water throughtput, and excessive organic debris present in the input water. Since the re-circulation systems have been installed and running for 2 months, the water in both filter systems has improved tremendously. The foul odor is gone, and the water is clear again. The details follow.

There have been 5 options for re-circulating water used here. Totally manual, an electronic timer, a modified ball valve, a modified standard hose bib, and a drip irrigation timer.  All five work. The modified standard hose bib was the most difficult to set up and the least professional – it is not shown, even though it does work.

The manual method (adding water from a bucket filled by a hand operated pitcher pump) and the electronic timer will work with a non-pressurized system. The manual method is the most time consuming and requires daily attention.

The electronic timer switch is the Amico DC 12V Digital LCD Power Programmable Timer Time Switch Relay 16A      sku 40037612     This timer will handle 16 amps.  We are also now testing out a PV array set up to charge and run small dc motors of the size used in the pumps on the recirculation systems shown here. So far, a 50 watt PV array produces waaayyyy more power than is needed to keep the motors running during the summer months when there is little or no rainfall. The recirculation is not really needed in the fall, winter, or spring, so the lack of sunshine is irrelevant.

Much more info as I get time. . .   .   right now “I got all the freaking work I need”.

This is the ball valve. It is in use on filter 4 along with the electronic timer, for test purposes only. Either this or the electronic timer will work alone. The extended arm on the ball valve allows very fine adjustment of flow rate.The electronic timer is not needed, we are just testing it out.

This is the programmable timer. It will work with or without a pressurized system. It just turns the motor off and on at specified times. Up to 17 choices in 24 hour time period. This is in use with filter 4. So far the timer works like a charm. The "manual" button allows the water to be turned on and off anytime without disturbing the programmed times.

this is a schematic of the timer circuit hookup. The battery symbol represents the 12 volt power supply for the motor and the timer. The timer must have the power supply hooked up before the relay inside it will function. The capacitor is necessary to keep the relay contacts from being burned by arcing as the motor has significant inductance.

This is the schematic of the filter 4 system that uses flow regulation and flow frequency control using the electronic timer switch.

This is the raindrip timer. It works with a pressurized system. This is in use on filter 5. It is set to allow flow for 1 minute every hour on the hour.

This is the schematic of the recirculation system with the raindrip timer.

Important:

We have been researching rain water harvesting laws for some time now. This is an almost impossible task; as each state’s website is different and the regulations are unbelievably complex. Legal assistance is needed to accurately interpret the laws, rules and regulations. Please see our previous posts for extensive info on rain water harvesting laws; but keep the following in mind:

There are 50 state governments (not counting the District of Columbia or the Philippines) and 3007 counties with some form of government in the U.S. and over 18 thousand cities/metropolitan areas and then there are the homeowner’s associations with covenants, and restrictions that are limited only by abiltiy to pay for legal assistance. These local laws may make rainwater harvesting against the law; even though it may be even encouraged by state governemnt.  It is not possible for us to ever get all of these micro-communities documented. The best we do here is the State and Federal regulations.

Just as an example of what we search through, this is Virginia’s water law page: approximately 1200 laws to search through– and that is after we took the time to actually find the page. Each state is different.

So far we have looked up rain water harvesting laws in: Arkansas, Kansas, South Carolina, Illinois, Wisconsin, South Dakota, New Jersey, Washington state, Oregon, Utah, Colorado.  What we found coincides very closely with the information in our original post regarding rain water harvesting in the U.S.

The pattern we are finding shows increasing freedom regarding rain water harvesting for the individual, along with, in some cases, increasing regulations depending on the intended use of the harvested rain water. Please note: neither I, nor anyone else here has studied law in college. We are not lawyers. To pay a lawyer to do this research would be cost prohibitive, to say the least.

We are reading these laws and regulations from the state government websites. There are links so each person can make their own judgement as to the meaning.

On October 20, 2011;  I wrote a bit on this blog about moss eating away at roof surfaces. Since then I’ve done more research. Moss does not “eat away” at your roof. Moss is a bryophyte. It does not have roots and gets its food from water and sunlight – not the substrate (the stuff it grows on). It eats away at nothing. Check the science. Its the stuff that often is present with moss (and often hidden by the moss) that does the damage; along with sunlight, below freezing weather, moisture and power washing. Sunlight, and high pressure power washing do way more damage to a roof than moss can ever do.

The original  post was a result of observing how the moss interacts with the rain water runoff from the roof, and I got carried away with the details. Since then, I’ve done more research. One important observation I have made here is that where the moss was most prevalent, the water was of the best quality. A new filter was added receiving water from an area on the roof with very little moss. Subsequently, that new filter was overwhelmed with debris and excessive organic contaminants. Also, I’ve actually gone up on the roof here to take a very close look at the moss growing there. The roofing material does “appear” to be slowly breaking down where the moss is growing; however it is also breaking down where the moss is minimal and the sunlight is maximum. So what’s up with this? Are the contractor’s who insist that moss eats away at your roof correct? Possibly. Moisture definitely does lots of damage – over time – and moss can hold moisture. I’ve had a roofing expert out here to inspect the roof. He said nothing about the moss being a big problem. He explained that the insulation under the roof in the attic, the ridge vent functionality and moisture present in the air are the biggest problems. Moss is an indicator of other problems, not a problem in itself.

Consider the links below:

https://en.wikipedia.org/wiki/Lichen

https://en.wikipedia.org/wiki/Moss

http://dmr-gutters.com/rf/moss.htm#composite

The last link is the most interesting from the point of discovering where the idea that “moss eats away at your roof” comes from. The person who has this website is an experienced contractor. At the top of the page that the link takes you to, you will discover his explanation of how “moss” destroys composition roofing. If you read it carefully, you will see that he already has seen and knows from experience what we have discovered from our academic research on this touchy topic. Now, read all three of these links and the previous post on this blog here for numerous other (scholarly) links and the truth of the matter will become obvious.  The moss is not what actually breaks down the roofing material; its what is present (usually) with the moss. Lichens, bacteria, moisture, organic debris, and sunlight are the issues that are most destructive to composition roofing material. The only thing that is obvious from a visual inspection however, is that when there is moss on a roof, the material breaks down quickly. The science described in the links above, including the links in the previous article on this blog, show that its not the moss that breaks down the roofing, and actually sunlight is more destructive to roofing material than moss or, moisture, or lichens.  Also, if you read the contractor’s website closely, you will see that he accurately describes the tremendous damage “power washing” does to a roof – it literally rips the sand off of the shingles exposing the petroleum based subsurface to the sunlight, which will break down that petroleum base in a few years. So, the scenario is typically this: A homeowner gets moss on their roof, calls a contractor to power wash the moss off. Then, 3 or 4 years later their roof fails. They blame the moss. Totally wrong. Prevarication of facts and big misunderstanding.

Now, from all this people get the idea that moss is really bad stuff. Moss killer is all over the place in the hardware stores. People put chemicals on their lawn to kill that nasty moss. Some people are smart, however. They have a moss instead of a lawn. Weeds seldom penetrate the moss and it does not really need watering here in the Pacific Northwest. Low maintenance, soft and pretty. Hmmmm.

If you keep the organic debris off of the roof, and sweep the moss with a stiff broom while the moss is wet and before it gets established, it is possible to keep the roof basically moss – free and poison – free, with minimum damage to the roof. This will also help to prevent the stuff (lichens and bacteria)  that really does “eat away at your roof” from ever getting started.

If anyone has information that shows the science here is wrong, or that my interpretation is wrong, please post it with a link to the source and we will change this post accordingly. No link, no change. Your are entitled to your opinion; but it will change nothing here.